3 2 SCIENTIFIC AGRICULTURE. 



constitution will convert a disagreeable or tasteless 

 fruit into one that is sweet and delicious. 



62. Starch and sugar differ from each other very 

 slightly in the number and proportion of their con- 

 stituent elements, while starch, cellulose, and gum 

 are the same in these respects. How the internal 

 structure or arrangement of these elements causes a 

 change in properties, we do not know. Starch forms 

 the larger portion of the seeds of most plants, and 

 especially of those used as food. Wheat, corn, rice, 

 and potatoes, when dry, are about two-thirds starch. 



63. Grape-sugar differs from starch by one equiva- 

 lent of water, that is, by the addition of a little water 

 chemically combined, starch becomes sugar. This 

 change takes place in seeds to some extent in the 

 process of sprouting, and is taken advantage of in the 

 manufacture of beer and whisky from barley and 

 corn. A lock of cotton, or even some sawdust, can 

 be changed into sugar suitable for manufacturing al- 

 cohol by dissolving it in strong sulphuric acid, dilut- 

 ing with water, and boiling for some time. 



64. Every green leaf is a tiny laboratory, where 

 by the aid of the sun's rays those changes are made 

 which give us wood, and starch, and sugar, and gluten, 

 and gum. To make these the plant uses carbon di- 

 oxide and ammonia, and water and other substances, 

 which enter the plant as food. 



65. The following table gives the composition of 

 various crops : 



